While the term overburden may refer to practically any amount of material lying over a valuable deposit, it tends to include hundreds of thousands of tons per mining site. Shallow mining, known as strip mining, may only have a few feet of sand or otherwise loose material to remove. More involved surface mining techniques like mountaintop coal removal and oil sands processing may require the excavation of hundreds of feet of overburden. Digging out 250 feet of rock, clay, and sand generates a far greater amount of overburden. Before any mining takes place, it is important to weigh the costs of removing and dealing with this overburden against the potential profit from the valuable material below. If there’s simply not enough profit potential, the mine could be a waste of energy. However, the answer isn’t to avoid the costs of containment for overburden. In fact, trying to save money by avoiding liners will only lead to higher remediation costs in the long run.
Comparing Volumes of Material
While there are a number of different formulas used to quickly or thoroughly determine the profit to cost ratio of a mine, all of them basically compare the two volumes of material. Understanding the potential value of the ore or coal is essential to starting the calculations. Once the potential of the seam or deposit is measured, the volume of overburden is measured and costs for its removal are figured. Ideal ratios of weight between overburden and valuable sand or raw ore vary depending on the value of the desired material. A low-grade coal deposit will need a far lower ratio than a high value mineral or ore. The thicker the layer of overburden, the more valuable the material below must be to justify the work.
Costs of Removal, Storage, and Containment
It is not just the raw ratio of overburden material to desirable ore that determines if a mining operation is worthwhile or not. The removal method needed to get the overburden out of the way also factors into the equation. For example, hard rock removal with blasting is far more costly than excavation with heavy equipment like bucket lifts alone. Although, removing a thin layer of hard rock could still cost less than excavating out hundreds of feet of loose sand that require specialty equipment. Don’t forget to factor in the costs of storage and containment. Unless there’s a hazardous waste dump nearby ready to receive such a large volume of material, the overburden will need onsite storage until it is time for reuse.
Lack of Containment Leads to Remediation Costs
Avoiding containment like geomembrane liners and berms will not save the mine money in the long run. While it may reduce upfront costs by decreasing the price of installing storage for the overburden material, the expense will come back in the end through remediation. Long-term environmental damage is all too likely if containment measures are avoided. Removing large amounts of contaminated soil, or covering the surface, only makes it harder to keep the mine profitable. Start off on the right foot with durable geomembrane liners that won’t let overburden materials or their leachates escape into the environment.
Invest in containment measures for overburden produced from any kind of mining or excavation work by choosing geomembranes from BTL Liners. Our reinforced polyethylene liners won’t rip or tear just because you’re piling on plenty of abrasive materials. Even the high petroleum content of many oil sand overburden mixtures won’t be a problem with our chemical-resistant products. Choose geomembrane liners you can trust.
